The objective of this study is to determine if non-aspirin, non-steroidal, anti-inflammatory drugs (NANSAIDs) reduce the risk of acute, first myocardial infarction. Because NANSAIDs, one of the most frequently prescribed classes of therapeutic agents, have anti-platelet properties similar to aspirin (ASA), their use increases the risk of bleeding complications both when used alone and when combined with the low doses of ASA used to prevent acute myocardial infarction (MI). However, NANSAID's anti-platelet properties might, like ASA, also make them effective in preventing MI. If so there would be no reason to risk bleeding complications by combining ASA with NANSAIDs for cardioprotection. Furthermore, the risk-benefit ratio of NANSAIDs themselves would be substantially improved. Despite animal data and clinical observation suggesting that NANSAIDs might reduce the risk of MI, a well-designed analytic study has yet to address this hypothesis. The proposed study is a population-based case-control investigation using the Delaware Valley Case-Control Network to determine the risk of MI in subjects recently exposed to NANSAIDs. All cases of first MI hospitalized in a defined geographic region will be identified over a period of 4 years and compared to controls who will be selected randomly from the same geographic region using random digit dialing. All cases and controls will undergo the same structured telephone interview within weeks of their identification. Information about recent NANSAID use and known and possible confounders will be obtained using state-of-the-art pharmacoepidemiologic techniques. In addition, a sample of subjects will have their prescription NANSAID use verified using claims data, and all cases will have their medical records reviewed to validate the occurrence of MI. Univariate and multivariate analyses will be performed to determine if NANSAIDs are associated with a reduced risk of MI after controlling for confounders. Dose and frequency response analyses also will be performed, and the effects of different types to NANSAIDs will be assessed both to examine the biological plausibility of the study hypothesis and to determine if specific dosing regimens or types of NANSAIDs have a greater potential for reducing the risk of MI. The investigators state that the results of this study will provide information needed both for physicians who must make appropriate decisions about therapies for patients who would benefit from both NANSAIDs and ASA and for scientists who must assess the risk-benefit ratio of one of the most commonly used medications today.